import java.util.*;


class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;
    }
}

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        scanner.close();
        HashSet<Character> hs = new HashSet<>();
        //write your code here......
        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            hs.add(ch);
        }
        for (char c : hs) {
            System.out.print(c);
        }
    }


    public ArrayList<ArrayList<Integer>> Print(TreeNode pRoot) {
        // write code here
        ArrayList<ArrayList<Integer>> list = new ArrayList<>();
        if (pRoot == null) {
            return list;
        }
        int height = height(pRoot);
        for (int i = 0; i < height; i++) {
            list.add(new ArrayList<>());
        }
        test(pRoot, 0, list);
        return list;
    }

    private int height(TreeNode pRoot) {
        if (pRoot == null) {
            return 0;
        }
        int h1 = height(pRoot.left);
        int h2 = height(pRoot.right);
        return Math.max(h1, h2) + 1;
    }

    private void test(TreeNode pRoot, int level, ArrayList<ArrayList<Integer>> list) {
        if (pRoot == null) {
            return;
        }
        test(pRoot.left, level + 1, list);
        test(pRoot.right, level + 1, list);
        list.get(level).add(pRoot.val);
    }


    public boolean isCompleteTree(TreeNode root) {
        // write code here
        return isW(root);
    }

    public boolean isW(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        TreeNode cur = root;
        queue.offer(root);

        while (cur != null) {
            cur = queue.poll();
            if (cur != null) {
                queue.offer(cur.left);
                queue.offer(cur.right);
            }
        }
        while (!queue.isEmpty()) {
            TreeNode is = queue.poll();
            if (is != null) {
                return false;
            }
        }
        return true;
    }
}